断層粘土中の石英粒子の表面構造による断層活動性の評価の試み ＩＩ 表面構造と断層の破砕様式および活動時期

Abstract

Surface textures of quartz grains taken from about 250 samples of fault gouges in faults in length in ranging from several meters to several tens of meters and faults extending several tens to several hundreds of kilometers in length are examined by means of the scanning electron microscope and are categorized into four gouges from I to IV, judging from the smoothness of the surface, degree of undulation and development of cavities, as mentioned in the previous paper. Based on surface features of quartz grains from faults for which the geological age of their movement is known, the groups I to IV are tentatively related to the age of formation of quartz grains and the period of formation of surface textures. River pattern, striations, granular fracture surfaces, and dimple-like textures are observed to appear on less corroded surfaces of quartz grains from fault gouges. Fractographic analysis of these surfaces of quartz grains should be a clue to revealing the mode of fracture of the fault movement which released the quartz grains into the fault gouge.